Internal valves are used in a variety of commercial and industrial applications to control fluid flow between a fluid storage container and another container, hose, pipeline, etc. Typically, internal valves are provided with an equalization member to equalize fluid pressure across the valve prior to fully opening the valve. The rate at which the fluid pressure equalizes across the valve is associated with the size of the valve and the fluid flow rate through the equalization member.
To equalize the pressure across known internal valves, these valves are provided with a stem having a cut-away portion or groove that varies the fluid flow rate through the equalization member depending on the position of the cut-away portion or groove relative to an aperture that fluidly couples the valve to the container, hose, pipeline, etc. Specifically, if the cut-away portion or groove is adjacent the aperture, the size of the fluid flow path is relatively large and, in contrast, if the cut-away portion or groove is at a distance from the aperture, the size of the fluid flow path is relatively small.
Different internal valves have different diameter apertures and different size stems. Accordingly, the diameter of the aperture is restricted by the size of the valve, and the amount of material that may be removed from the stem to create the cut-away portion or groove is restricted by the size of the stem. Generally, removing material from a body decreases its structural integrity and, therefore, the amount of material that can be removed from the stem is limited to an amount that enables the structural integrity of the stem to be maintained while providing a fluid flow path to equalize the pressure across the valve. As a result, the speed at which known internal valves can be fully opened is limited by the amount of material that can be removed from the stem.
Additionally, the cut-away portion or groove creates a non-cylindrical surface on the stem. Due to manufacturing tolerances, the stem may rub against the surface defining the aperture as the stem is moved. Unlike smooth cylindrical surfaces, the non-cylindrical surface has edges that may wear a groove(s) in the surface defining the aperture, which decreases the useful life of the valve. Additionally, in some instances, the engagement between these edges and the surface defining the aperture causes the valve to malfunction.